In serial printers, there is typically utilized a circular print disc positioned parallel to the plane of a surface to be printed, and containing a character font disposed at angular increments around the face of the disc. To print any desired character, the print disc is rotated by a driving mechanism to an angular position corresponding to that character. The character is then hammered into contact with an inked ribbon and the surface to be printed.
Largely because of space constraints, it has been a problem in known printers to remove and/or replace the print disc. In the prior art, removal is typically effected by rotating the entire driving mechanism away from the printing surface in order to allow the print disc to be slipped off a supporting shaft. This is an extremely cumbersome procedure requiring bearings, hinges, and other mechanical elements, all of which must be kept in alignment for proper operation of the printer.
In accordance with the illustrated preferred embodiments, the present invention provides a print disc which can be removed from and replaced on a supporting rotatable member in a direction transverse to the rotation axis of the rotatable member. The print disc may therefore be slipped into and out of position between the driving mechanism and the printing surface without rotation of the drive or any other major disturbance of the apparatus. To achieve this result, a guide is provided which is affixed to the end of a drive shaft. The print disc may then be slipped onto the guide in a direction perpendicular to the shaft axis. Preferably, the guide includes tensioning elements to retain the print disc in position.